Paint gun



i, July '1, 1 42. RKLSTEEL 2,289,31

PAINT GUN Filed Nbv. 22, 1940 INVENTOR;

; flzdezykk 16. 512% BY; M7

variations in the size whenother factors are Patented July "I, 1942 li -Fr es] PAINT GUN Frederick K. Steel, Chica .Ill.,assignor-to Asp m J 1 sociation of American. Railroads, Washington, D. 0., an unincorporated association Application November 22, 1940, Serial No. 366,753.

7 Claims.

flaws in the rails of a railroad track it is the presenttpractice torun a car along the track with detecting equipment which includes a. paint gun that automatically shoots a spot ofpaint on the rail adjacent a flaw. For various reasons it is desirable that the spot of paint applied by the gun be reasonably small, say in the neighborhood of one and one-halt inches in diameter or smaller. Heretofore it has been necessary to rely either upon a complicated metering device or upon a very short, actuating impulse for the gun. However, it hassometimes been ,difiiculttomake the actuating impulses sufiiciently short, and therefore the paint spots have sometimes been undesirably large.

Small spots are very desirablesfor the'pur- In detecting hidden 7 Additional advantages and objects of the invention will be apparent from the following" description and from the drawing, lnwhich:

The figure is in part acircuit diagram and in part alongitudinal sectional view of a paint gun constructed in accordance with this invenpose of showing flaws which are close to another flaw or a rail joint, since large spots would be merged together and appear as one. The need for some further means] for limiting the size of the paint spots has beenincreased by the provision of two detector :circuits, bothoperating the same paint gun, with the resultthat the gun would shoot twospots'ior each fissure instead of one. This increases the chance that the spotsfor two different fissures will be merged with resulting confusion.

It has been thepracticeheretofore to operate the valve of the paint gun magnetically, the gun being surrounded by a solenoid coil and the valve and its shank being magnetic and being positioned to be drawn open by the solenoid. According to the present invention, the solenoid impulse does not merely drawthe valve open and then permit it to be ,closed by a spring, remaining open during the entire moveadjacent a hidden flaw I4,

' and 49 respectively, mounted 20 and 21, respectively,

ment back and forth; instead, it provides a supplemenitjagl valve which is closed by the opening.

movement of, the. main valve so that a continuous flow fromihe. time the main valve opens until it is again f closed [is] prevented. The two valves are mounted on opposite ends of a single reciprocating shank and one of; them isadjustable thereon so that the length of stroke between theopeninglof one valve and the closing of the other may be regulated. This facilitates adjustment ofthe approximate maximum size of the paint spot. Reference is made to the approximate maximumf size of paint spot because of the fact thatvarying conditions such as temperature, viscosity of the' paint, and air pressure applied to it will result insubstantial of thepaint spot even constant;

paint gun relays 28 tion, the approximate position of the paint gun adjacent the [rail being shown on a smaller scale in another part of the figure.

A preferred form of' I chosen for illustration and descriptiomin compliance with section 4888 of the Revised Statutes, but persons skilled in the art will readily perceive other means for accomplishing the same results; and the claims are therefore to be construed as broadly as possible, consistent with the prior art.

In thefigure the invention has'been illustratcd diagrammatically except for the con:- struction of the paint gun H, which is shown in detail. As seen at the figure, the paint gun is intended for the purpose of shooting spots of paint l2 on a rail l3 which is detected by either ofth detecting units [6 or H. Each of the detecting units comprises a pair of coils 18 on suitable cores which are moved lengthwise along the rail immediately adjacent to the top thereof. According to one system of [detection, a-current is passed through the rail and the deflection of thecurrent by the flaws causes an impulse to be generated in the coils l8 and I9 as they pass over the flaw. According to another system, the rail is first magnetized and then the magnetizing force is removed with the result that, in effect, the flaws are polarized and as a result an impulse is generated in the coils -l8 and H? as they pass over the flaw. The coils I8 and i 22 and 23 respectively. These amplifying units 26 and 2! and to paint gun relays 28 and 29.. The pen relays 26 and 21 actuate separate pens but the and 29 operate a paint gun'and in fact may operate a single not actuatedby the coil 32,

armature 3i- The armature connecting the paint gun II, or, more specie fically, its solenoid coil 32, to a source of power The coil 32 opcloses the outlet valve port 35, being pressed against the seat thereof by spring 3 l. The magnetic force genthe invention "has been left-hand'*portion of the 9 are connected to amplifying units 7 single 3i closes a circuit 34 which, when erated by the coil 32 retracts the plunger 33, thus opening the port 36 so that paint supplied through conduit 38, under pressure from a source of compressed air, not shown, shoots out through the port 36 and the nozzle 39 to form a spot of paint I2 on the rail [3.

The two spots of paint shown on the Figure 25 are caused by a single flaw [4 as the successive detector units [6 an l ll pass gyerit. h lt is evident that'if 'anther -fiavv were elose to? the flaw M or if the new H w e're'close to a rail joint, additional spots of paint might be applied. so close to one of the spots 12 shown that the two would merge and it would be difficult to tell whetherreasonably small. If the armature 3| were held closed for a substantial length of time and paint were allowed to flow freely through the port 36 during all .the time that. the armature-3| was closed, 'the ,resulting'paintfspot' would be muchtoo large..}Heretofore {there have been various proposals for avoiding .thisfdifhculty by various expedient's' such as a'ccurajtely; controlling the dependably small. Although it is not. of a uniform size, since its size depends on the air pressure and viscosity of the paint, it has nevertheless been found to make completely unnecessary the metering devices which have sometimes been used and which are considerably more expen- SlVe.

The gun of this invention has been found to be very satisfactory. It is economicalto manufacture and satisfactorily.restricts the size of the paint spots to a reasonable size while at the same time making completely unnecessary any length ,of time duringf -which the circuit; to, the coil 32 could be .c losed;.or accurately ;metering the amount of paint'whic h would beexpelled. 1 According to the. present invention the-problem".

is solved in an entirelydifierent and much-Si m:-

pler mamaptpmvrdmg adouble acting plunger 33 which shuts oifth'eflow of paint very quickly after openinggthe valve port-36.

To. thisend the plunger. 33, comprises, in a d-' dition to' the'valvehead ul-a shank or stem {H to which: it is'secu-red and a second-valve head 42 screwed on the shank! l. and preferably locked in a given position thereon by a;lock nut 43. As

the coil 32,retracts,the plunger. 33,;raising the;

valve head 34" from itsval ve seat'; it thrusts the valve head 42; against an inlet valve seat 44, thus closing the inlet valve; No more paint will flow no matter how long .the circuit for the 32,

remains closedand hence there is no danger of having the paint spots l-2 excessively large, It might be -suppos,edthat. .when. the coil .32

i de-energized, another shot of paint would be expelled from the paint gun as the plunger 33 moved from the inlet-closing position to its'normal position in which it closes the outlet port or valve 36. A gun madeii'n. accordance with this invention hasbeen inpractical use, however, and apparently there isonly one shot of paint for each energization of the.coil-3 2. The

probableexplanation of thisis. that enough of the paint flows out when the plunger is. raised.

so as to leave a little air spacewithin the .valvev 0- and sealing engagement with the outlet valve time to fill the space and it does {not have time to shoot past the plunger through the nozzle 39. v I

The length of time during which the outlet ports 44 and 361are both open {can be 33 and discharge inlet. and I.

regulated by adjusting thev'alvehead 41' on the stem 4|, looking it in its' adjustedposition by f lock nut 43. ,The separation of the two valve I heads determines the length of strokeof the plunger and hence the, length. of time, during which both valves are open. Since both valves are open for only a short time, the paint spotis special electrical or mechanical features tending '-"t0.' accurately time the closure of the circuit or accurately measure and segregate the amount of pai'ntjto be discharged.

' cl m 1. A paint gun for applying a spot of paint of approximately-limited size to a rail adjacent a spaced fromithe inlet valve seat, and a, coil surrounding the-valve chamber for shifting the -.-plunger to move one valve away from the outlet valve-seat and with the same stroke close the inlet valve seat with the other valve, one of said valves being adjustably'positioned with respect.

to the-other to control the length of stroke between the opening of one valve and the closing of the other.

2. A paint gun forapplying a spot of paint of approximately; limited size to a rail adjacent a flaw therein, comprising a main body forming a valve chamber having alined inlet and outlet valve'seats, means for supplying paint to the chamber. through the. inletseat, a magnetic plunger within the valve chamber having a'valve on each end thereof, a spring normally pressing one valve into closing and sealing engagement with the outlet; valve seat, the other valve being positioned adjacent to but spaced from the inlet valve seat, and a coil surrounding the valve chamber for shifting the plunger to movepne valve away from the outlet valve seat and with the same stroke close the inlet valve seat with the other valve.v

3. A paint gun for applyinga spot of paint of approximately limited size to a rail adjacent a flaw therelmcomprising a main body forming a valve chamber having alined inlet and outlet valve seats,x-a magnetic plunger within the valve chamber having a valve on each end thereof, a spring normally pressing one valve into closing seat, the other valve being positioned adjacent to but spaced from the inlet valve seat, and a coil surrounding the valve chamber for shifting I the plunger to move one valve away from the outlet valveseatand with the same stroke close the inlet valve seat with the other valve, the

. valve seats, a magnetic plunger within the valve chamber having a valve on each end thereof, a spring normally pressing one valve into closing and sealing engagement with the outlet valve seat, the other valve being positioned adjacent to but spaced from the inlet valve seat, and a coil surrounding the valve chamber for shifting the plunger to move one valve away from the outlet valve seat and with the same stroke close the inlet valve seat with the other valve, the closing of the inlet valve seat operating to cut ofi from the valve chamber all supply of pressure above atmospheric pressure, one of said valves being adjustably positioned with respect to the other to control the length of stroke betweenthe opening of one valve and the closing of the other and the amount of paint that will be discharged under given conditions of viscosity, pressure, and magnetic force.

5. A paint gun for applying a spot of paint of 7 approximately limited sizeto a rail adjacent a flaw therein, comprising a main body forming a surrounding the valve chamber for shifting the plunger to move one valve away from the outlet valve seat and with the same stroke close the inlet valve seat with the other valve, the magnetic plunger comprising a rod and the valve at one end thereof being threaded on said rod to be adjustable with respect thereto, and a lock nut l flaw therein, comprising a main body forming a valve chamber having alined inlet and outlet valve seats, means for supplying paint to the chamber through the inlet seat, a magnetically operable plunger within the valve chamber having a pair of valves facing outwardly from an intermediate point thereof, a spring normally pressing one valve into closin and sealing engagement with the outlet valve seat, the other valve being positioned adjacent to but spaced from the inlet valve seat, and a magnetic coil for shifting the plunger to move one valve away from the outlet valve seat and with the same stroke close the inlet valve seat with the other valve, one of said valves being adjustably positioned with respect to the other to control the length of stroke between the opening of one valve and the closing of the other.

7. A paint gunfor applyin a spot of paint of approximately limited size to a rail adjacent a flaw therein, comprising a main body forming a valve chamber, having only two openings therefrom, said openings being formed in generally opposed inlet and outlet valve seats, a magnetic plunger within the valve chamber having gen-v erally opposed valves adapted to close said openings alternatively, a spring normally pressing one valve into closing and sealing engagement with the outlet valve seat, the other valve being positioned adjacent to but spaced from the inlet valve seat, and magnetic means for shifting the plunger to move one valve away from the outlet valve seat and with the same stroke close the inlet valve seat with the other valve, the closing of the inlet valve seat operating to cut on" from the valve chamber all supply of pressure above atmospheric pressure, and means for adjusting the relationship between the spacing of the valves and the spacing of the valve seats to control the length of stroke between the opening of one valve and the closing of the other and the amount of paint that will be discharged under given conditions of viscosity, pressure, and magnetic force.

, FREDERICK K. STEEL. 

